Positive electrode and electrochemical apparatus

Abstract

A positive electrode, including a current collector and a positive electrode active material layer provided on the current collector, the positive electrode active material layer including a lithium transition metal composite oxide, where in a direction parallel to a plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dp, and in a direction perpendicular to the plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dv, satisfying: 1.1≤ Dp/Dv ≤2.3.

1 . A positive electrode, comprising:
 a current collector;   a positive electrode active material layer provided on the current collector,   wherein the positive electrode active material layer comprises a lithium transition metal composite oxide; and   in a direction parallel to a plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dp, and in a direction perpendicular to the plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dv, wherein 1.1≤Dp/Dv≤2.3.   
     
     
         2 . The positive electrode according to  claim 1 , wherein 5 μm≤Dp≤25 μm. 
     
     
         3 . The positive electrode according to  claim 1 , wherein
 0.8≤(Dp+Dv)/2D N 50≤1.25, wherein D N 50 is a median particle size of the lithium transition metal composite oxide.   
     
     
         4 . The positive electrode according to  claim 1 , satisfying at least one of the following conditions a) and b):
 a) the lithium transition metal composite oxide has an R-3m space group structure; and the lithium transition metal composite oxide comprises Li x1 Ni y1 Co z1 Mn k Z q O b-a T a ,   wherein Z comprises at least one selected from the group consisting of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb and Ce,   T is a halogen, and
   0.2< x 1≤1.2, 0 ≤y 1≤1, 0 ≤z 1≤1, 0 ≤k≤ 1, 0 ≤q≤ 1, 1 ≤b≤ 2 and 0 ≤a≤ 1;
 
   b) the lithium transition metal composite oxide has a P63mc space group structure; and   the lithium transition metal composite oxide comprises Li x2 Na z2 Co 1-y2 M y2 O 2±n X n , wherein 0.6<x2<0.95, 0≤y2<0.15, 0≤z2<0.03, and 0≤n≤0.2,   M comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr and Zr, and   X is a halogen.   
     
     
         5 . The positive electrode according to  claim 1 , wherein the lithium transition metal composite oxide has a long-axis average particle size D 1  and a short-axis average particle size D 2 , and 1.4≤(D 1 /D 2 )≤5.5. 
     
     
         6 . The positive electrode according to  claim 5 , wherein 7 μm≤D 1 ≤28 μm. 
     
     
         7 . An electrochemical apparatus, comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises:
 a current collector;   a positive electrode active material layer provided on the current collector,   wherein the positive electrode active material layer comprises a lithium transition metal composite oxide; and   in a direction parallel to a plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dp, and in a direction perpendicular to the plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dv, wherein: 1.1≤Dp/Dv≤2.3.   
     
     
         8 . The electrochemical apparatus according to  claim 7 , wherein 5 μm≤Dp≤25 μm. 
     
     
         9 . The electrochemical apparatus according to  claim 7 , wherein 0.8≤(Dp+Dv)/2D N 50≤1.25, wherein D N 50 is a median particle size of the lithium transition metal composite oxide. 
     
     
         10 . The electrochemical apparatus according to  claim 7 , satisfying at least one of the following conditions a) and b):
 a) the lithium transition metal composite oxide has an R-3m space group structure; and the lithium transition metal composite oxide comprises Li x1 Ni y1 Co z1 Mn k Z q O b-a T a , wherein Z comprises at least one selected from the group consisting of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb and Ce, T is a halogen, and 0.2<x1≤1.2, 0≤y1≤1, 0≤z1≤1, 0≤k≤1, 0≤q≤1, 1≤b≤2 and 0≤a≤1;   b) the lithium transition metal composite oxide has a P63mc space group structure; and the lithium transition metal composite oxide comprises Li x2 Na z2 Co 1-y2 M y2 O 2±n X n , wherein 0.6<x2<0.95, 0≤y2<0.15, 0≤z2<0.03, and 0≤n≤0.2, M comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr and Zr, and X is a halogen.   
     
     
         11 . The electrochemical apparatus according to  claim 7 , wherein the lithium transition metal composite oxide has a long-axis average particle size D 1  and a short-axis average particle size D 2 , and 1.4≤(D 1 /D 2 )≤5.5. 
     
     
         12 . The electrochemical apparatus according to  claim 11 , wherein 7 μm≤D 1 ≤28 μm. 
     
     
         13 . The electrochemical apparatus according to  claim 7 , wherein when the electrochemical apparatus is charged to 4.6 V, an X-ray diffraction spectrum of the positive electrode has at least a characteristic peak P 1  and a characteristic peak P 2  in a range of 17° to 20°, wherein a peak intensity I 1  of the characteristic peak P 1  is greater than a peak intensity I 2  of the characteristic peak P 2 ; and
 when the electrochemical apparatus is discharged to 3.0 V, an X-ray diffraction spectrum of the positive electrode has a characteristic peak P 3  in a range of 17° to 20°, wherein the characteristic peak P 3  has a peak intensity I 3  and (I 1 −I 2 )≤I 3 ≤(I 1 +I 2 ). 
 
     
     
         14 . The electrochemical apparatus according to  claim 13 , wherein a ratio I 1 /I 3  is not less than 0.8. 
     
     
         15 . The electrochemical apparatus according to  claim 7 , wherein when the electrochemical apparatus has undergone 8 charge and discharge cycles in a range of 3.0 V to 4.6 V and is discharged to 3.0 V, a highest peak of an X-ray diffraction spectrum of the positive electrode having undergone the cycles has a peak shift of no greater than 0.1° with respect to the positive electrode without undergoing the cycles; and a change rate of peak width at a half height of the highest peak is below 5%. 
     
     
         16 . The electrochemical apparatus according to  claim 7 , wherein when the electrochemical apparatus is discharged to 3.0 V, a surface of the negative electrode has strips. 
     
     
         17 . An electronic apparatus, comprising an electrochemical apparatus, the electrochemical apparatus comprises a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises:
 a current collector;   a positive electrode active material layer provided on the current collector,   wherein the positive electrode active material layer comprises a lithium transition metal composite oxide; and   in a direction parallel to a plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dp, and in a direction perpendicular to the plane on which the current collector is located, an average particle size of the lithium transition metal composite oxide is Dv, wherein: 1.1≤Dp/Dv≤2.3.   
     
     
         18 . The electronic apparatus according to  claim 17 , wherein 5 μm≤Dp≤25 μm. 
     
     
         19 . The electronic apparatus according to  claim 17 , wherein 0.8≤(Dp+Dv)/2D N 50≤1.25, wherein D N 50 is a median particle size of the lithium transition metal composite oxide. 
     
     
         20 . The electronic apparatus according to  claim 17 , wherein the lithium transition metal composite oxide has a long-axis average particle size D 1  and a short-axis average particle size D 2 , and 1.4≤(D 1 /D 2 )≤5.5.